Taaffeite
Encyclopedia
Taaffeite (ˈtɑːfaɪt; BeMgAl4O8) is a mineral named after its discoverer, Count Edward Charles Richard Taaffe
(1898–1967) who found the first cut and polished gem
in November 1945. As such, it is the only gemstone to have been initially identified from a faceted stone. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel
. For many years afterwards, it was known only in a few samples, and is still one of the rarest gemstone minerals
in the world.
Since 2002, the International Mineralogical Association
-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.
or something new; he also offered to write it up in Gemmologist.
, magnesium
and aluminium
, making taaffeite the first mineral to contain both beryllium and magnesium as essential components.
The confusion between spinel and taaffeite is understandable as certain structural features are identical in both. Anderson et al., classified taaffeite as an intermediate mineral between spinel and chrysoberyl
. Unlike spinel, taaffeite displays the property of double refraction that allows distinguishing these two minerals.
s alongside fluorite
, mica
, spinel and tourmaline
. This extremely rare mineral is increasingly found in alluvial deposits in Sri Lanka and southern Tanzania, as well as lower grade taffelite in limestone sediments in China.
Edward Charles Richard Taaffe
Count Edward Charles Richard Taaffe , knowns as Richard, was the Irish gemmologist who found the first cut and polished taaffeite in November 1945...
(1898–1967) who found the first cut and polished gem
Cut (gems)
When a gemstone is desired to be used in jewelry, it is cut depending on the size and shape of the rough, as well as the desired piece of jewelry to be made. As a rule of thumb, a cut gemstone will reduce the mass by about 50 percent....
in November 1945. As such, it is the only gemstone to have been initially identified from a faceted stone. Most pieces of the gem, prior to Taaffe, had been misidentified as spinel
Spinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
. For many years afterwards, it was known only in a few samples, and is still one of the rarest gemstone minerals
Gemstone
A gemstone or gem is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments...
in the world.
Since 2002, the International Mineralogical Association
International Mineralogical Association
The International Mineralogical Association is an international group of 38 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 4000 plus known mineral species...
-approved name for taaffeite as a mineral is magnesiotaaffeite-2N'2S.
Discovery
Taaffe bought a number of precious stones from a jeweller in November 1945. Upon noticing inconsistencies between the taaffeite and spinels, Taaffe sent some examples to B. W. Anderson of the Laboratory of the London Chamber of Commerce for identification on 1 November 1945. When Anderson replied on 5 November 1945, he told Taaffe that they were unsure of whether it was a spinelSpinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
or something new; he also offered to write it up in Gemmologist.
Properties
In 1951, chemical and X-ray analysis confirmed the principal constituents of taaffeite as berylliumBeryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, making taaffeite the first mineral to contain both beryllium and magnesium as essential components.
The confusion between spinel and taaffeite is understandable as certain structural features are identical in both. Anderson et al., classified taaffeite as an intermediate mineral between spinel and chrysoberyl
Chrysoberyl
The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4. The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely...
. Unlike spinel, taaffeite displays the property of double refraction that allows distinguishing these two minerals.
Formation and occurrence
Taaffeite occurs in carbonate rockCarbonate rock
Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite and dolostone, which is composed of the mineral dolomite .Calcite can be either dissolved by groundwater or precipitated by...
s alongside fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
, mica
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...
, spinel and tourmaline
Tourmaline
Tourmaline is a crystal boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gem comes in a wide variety of colors...
. This extremely rare mineral is increasingly found in alluvial deposits in Sri Lanka and southern Tanzania, as well as lower grade taffelite in limestone sediments in China.